Recovery of an i960 printhead!

[turbguy]

A long story, some of which might help others...bear with me.

I picked up a used i960 via eBay real cheap. The description gave me every indication that a tube came loose from the parking (purge) pad. Description contained the following text:

"This printer is not working... I believe there is something wrong with the printhead despite efforts to clean it... the quality kept getting worse until nothing was getting on the page any more. Otherwise it's working fine (paper passes through etc...)"

After receipt, I applied Windex to the parking pad. Sure enough, the parking pad would not hold a standing pool of Windex. It would drain away. This indicates a leak in the purge system. I popped off the top cover, and found the small hose at the rear of the pad had slipped off it's nipple. Since I had the unit open, I removed the peristaltic pump and cleaned it out (it was not clogged). Using fine needle nose pliers, I pushed the loose hose back on the pad and went into service mode. I forced a full clean, then forced a service test print.

IT WORKS!! BUT...NO LIGHT MAGENTA! (all refilled OEM carts, Hobbicolor inks, installed. All carts work great in another printer).

I soaked the printhead for for several days in Windex, then forced air though the inlets using a "turkey-baster" (Tube fits over the inlet screen, seals well around the cart gasket, air pressure being applied by hand on the rubber bulb). Air and fluid was found to pass freely through each of the lines of nozzles on every one of the six colors.

I dried the printhead and re-installed it, and forced a cleaning cycle.

I forced another service test print, STILL no light magenta!

Disappointed and thinking the printhead was toast, I pooled a puddle of windex on the parking pad, and ran another service test print.

HEY!!! THERE ARE TRACES OF DISCOLORED INK IN THE LIGHT MAGENTA POSITIONS!! THE PRINTHEAD IS FIRING IN LIGHT MAGENTA!! THE LIGHT MAGENTA NOZZLES HAD PICKED UP SOME STAINED FLUID FROM THE POOL LEFT ON THE PARKING PAD!!


I forced another cleaning cycle, and another service test print, all traces in the light magenta GONE!!

I pulled the printhead and pushed it against tissue. GUESS WHAT, five clear lines of color, one missing in the light magenta position. WTF?? Why isn't the Light Magenta getting any ink? Air and cleaning fluid can be forced through easily through all channels...

I replaced the gasket under the light magenta cart with a known good gasket. Forced Cleaning and a Service Test Print. Still no Light Magenta. Pulled printhead and did tissue test again. Still missing ink at the light magenta nozzles. Hmmm.....

With the cover off, I decided to re-install the printhead and apply a light downward force on the light magenta cart (and printhead) during another cleaning cycle with my finger....and GUESS WHAT!! ANOTHER SERVICE TEST PRINT SHOWS ALL NOZZLES IN LIGHT MAGENTA FIRING AND PRINTING!! HEY!!! AND further cleanings and test prints continue to work well!! The printhead is fine!

It appears that the parking pad is not being forced strongly enough against the printhead to form a good enough seal to reliably purge all six colors!

More investigation to do. The rubber rectangular gasket around the parking pad visually is perfect and fits well.

Anyone have any ideas??? I think I need to retest some other used prinheads I have that lost one color.....

Wayne

 

[Emulator]

Hi turbguy

Very interesting to read.

If there is an air leak around the parking gasket, the downward force on the printhead caused by the suction applied will be lost. This might be a significant part of the sealing process.

Regards

Ian